1. Field of the Invention
The present invention relates to a semiconductor memory device, and more particularly, to a multi-bank semiconductor memory device that is capable of varying a driving capability of a voltage driving circuit according to the number of accessed banks.
2. Description of the Background Art
As shown in FIG. 1, a conventional multi-bank semiconductor memory device includes a memory 10 having 16 banks, two bank address decoders 12 and 14, a controller 16 and a voltage generator 18.
The bank address decoder 12 decodes active bank addresses ABA0xcx9cABA3 and generates bank precharge signals BAC0-BAC15. The bank address decoder 14 decodes precharging bank addresses PBA0xcx9cPBA3 and generates bank precharge signals BPR0-BPR15.
RACC and RPRE respectfully correspond to a low access signal and a low precharge signal, which are RAS signals of DRAM. That is, the RACC performs the same function as a negative edge of the RAS signal, and the RPRE performs the same function as a positive edge of the RAS signal.
The controller 16 receives bank access signals BAC0xcx9cBAC15 and BPR0-BPR15 outputted from the two bank address decoders 12 and 14, and a driving enable signal DREN for driving the voltage generator 18 according to the bank precharge signals BPR0xcx9cBPR15.
As shown in FIG. 2, the controller 16 includes a plurality of latches (LAT1xcx9cLATn) and one AND gate AD1. An initial state of the latches (LAT1xcx9cLATn) is determined by a power up (PWRUP) signal.
The voltage generator 18 generates every power supply voltage VDD required for a memory device and includes one standby driving circuit 18-1 and a plurality of active driving circuits 18-2xcx9c18-n 
The standby driving circuit 18-1 is continuously operated, while the active driving circuits 18-2xcx9c18-n are operated according to the driving enable signal DREN outputted from the controller 16.
The operation of the multi-bank semiconductor memory device of the conventional art constructed as described above will now be explained.
Two bank address decoders 12 and 14 are synchronized by the low access signal RACC or the low precharge signal RPRE and decode an inputted bank address. Then, the two bank address decoders 12 and 14 generate bank access signals BAC0xcx9cBAC15 and bank precharge signals BPR0xcx9cBPR15, respectively.
That is, in reading/writing operations of the memory 10, the bank address decoder 12 decodes the bank addresses ABA0xcx9cABA3 synchronized with the low level low access signal RACC and outputs the bank access signals BAC0xcx9cBAC15 to the controller 16.
Meanwhile, in precharging of the memory 10, the bank address decoder 14 decodes the bank addresses PBA0xcx9cPBA3 synchronized with the high level low precharge signal RPRE and outputs bank precharge signals BPR0xcx9cBPR15 to the controller 16.
The controller 16 receives the bank addresses ABA0xcx9cABA3 or the bank precharge signals BPR0xcx9cBPR15 of each bank, and generates the driving enable signal DREN for driving the voltage driving circuits 18-2xcx9c18-n of the voltage generator 18.
Namely, the controller 16 includes latches LAT1xcx9cLATn indicating whether 16 banks are accessed or precharged and an AND gate AD1 for generating the driving enable signal DREN when at least one bank is accessed.
When an access signal of a specific bank is inputted, the controller 16 sets the latch, and conversely, when a precharge signal is inputted, the controller resets the latch. At this time, the power-up (PWRUP) signal serves to reset the initial state of the latches LAT1xcx9cLATn.
Accordingly, during an interleaving operation, since a plurality of banks are accessed, the latches LAT1xcx9cLATn are set according to the number of accessed as banks. That is, the number of set latches indicates the number of banks currently performing an interleaving operation.
The voltage generator 18 operates every active voltage driving circuit 18-2xcx9c18-n according to the driving enable signal DREN outputted from the controller 16 and generates a power supply voltage VDD required for the memory device. At this time, the standby driving circuit 18-1 is operated all the time.
The conventional multi-bank semiconductor memory device, however, has the following problems.
That is, first, the bank addresses ABA and PBA inputted in synchronization with the low access signal RACC or the low precharge signal RPRE are decoded by the respective bank address decoder 12 or 14 and inputted to the controller 16. Accordingly, a delay time occurs before the driving enable signal DREN of the voltage generator 18 is generated. Such time delay causes delay in the response of the voltage generator 18, causing an unstable operation of the memory.
Second, as the number of banks is increased in the memory 10, the bank addresses decoded by the bank address decoders 12 and 14 are increased to cause a problem that a routing area is enlarged.
Third, as the number of banks of the memory 10 is increased, the number of logic gates in the controller 16 and the input number of the logic gates are increased. Then, a lay-out area of the controller 16 is accordingly increased, serving as a factor delaying generation of the driving enable signal DREN.
Fourth, since the voltage driving circuits included in the voltage generating circuit are divided into two types of circuits including a standby circuit and an active circuit, if the number of banks for performing an interleaving operation is increased, it is difficult to suitably cope with it. The reason for this is that the number of the active driving circuits should be increased according to the number of the banks for performing the interleaving operation.
Fifth, if even one bank of the voltage generating circuit is accessed, every active driving circuit is operated. Thus, power is unnecessarily consumed.
Therefore, an object of the present invention is to provide a multi-bank semiconductor memory device that is capable of varying a driving capability of a voltage generator according to the number of active banks.
Another object of the present invention is to provide a multi-bank semiconductor memory device that is capable of stably operating a memory by increasing a response speed of the voltage generator.
A further object of the present invention is to provide a multi-bank semiconductor memory device that is capable of almost constantly maintaining a lay-out area regardless of the number of banks performing an interleaving.
Still another object of the present invention is to provide a multi-bank semiconductor memory device that is capable of optimizing a power consumption by varying the number of active driving circuits according to the number of active banks.
To achieve these and other advantages one embodiment of the invention includes a semiconductor device including a memory having memory banks and generating a first signal and a second signal; a voltage generator having a plurality of driving circuits and generating a power required for operation of the semiconductor memory device; and, a counter for receiving a first signal and a second signal and generating a count value and a corresponding driving signal for driving a first number of active driving circuits of the plurality of driving circuits such that the first number of active driving circuits is variable.
The counter counts the first signal and the second signal to generate the drive signal. Also, when a number of memory banks N of the memory banks in the memory are active, the driving signal has a value of logN bit. Further, the first signal is a low access signal, and the second signal is a low pre-charge signal.
The first number of active driving circuits may be equal to the count value determined by the counter. Also, the first number of active driving circuits may be sequentially driven according the count value determined by the counter. On the other hand, the first number active driving circuits may be variably driven according the count value determined by the counter.
In a second embodiment, a semiconductor device includes a multi-bank memory providing a first signal and a second signal; a voltage generator having a plurality of active driving circuits and generating a power required for the semiconductor device; and, an up/down counter for counting the first signal and the second signal and generating a multi-bit driving signal to drive a variable number of the active driving circuits.
The first signal is a low access signal and the second signal is a low pre-charge signal and generates a drive signal. Also, when the maximum number of banks performing an interleaving is xe2x80x98Nxe2x80x99, the drive signal may have a value of log N bit.
The active driving circuits may be sequentially driven according to a count value of the up/down counter. Also, the active driving circuits may be variably driven according to a count value of the up/down counter.
In a third embodiment, a method of operating a multi-bank semiconductor memory device includes outputting a first signal and a second signal from a multi-bank memory wherein the first signal and the second signal representing at least one active memory bank in the memory. A count value and corresponding driving signal are generated by counting the first signal and the second signal. Also, a number of active circuits are driven in a voltage generator for a semiconductor memory device using the driving signal such that the number of active circuits is variable.
Further, the step of driving the number of active driving circuits may include variably driving the number active driving circuits according the count value. On the other hand, the step of driving the number of active driving circuits may include sequentially driving the number of active driving circuits according to the count value. Further, the step of driving the number of active driving circuits may include driving a first number of active driving circuits that is equal to the count value determined by an up/down counter.
Lastly, the step of generating a count value and corresponding driving signal may be performed by an up/down counter.
These and other objects of the present invention will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.